Wide band tuner

ABSTRACT

When changeover switch ( 26 ) selects the output of L band filter ( 23 ), changeover switch ( 28 ) is turned off and mixer ( 29 ) is operated as an amplifier such that the oscillation frequency of local oscillator ( 31 ) is controlled based on data fed to data terminal ( 37 ) and a channel selection can be performed in mixer ( 32 ). When changeover switch ( 26 ) selects the output of V band filter ( 25 ), changeover switch ( 28 ) is turned on and a channel selection is performed based on data fed to data terminal ( 37 ) in mixer ( 29 ). With this arrangement, the need for a tuning filter is eliminated and a broadband tuner not requiring manpower for adjustments can be provided.

TECHNICAL FIELD

[0001] The present invention relates to a broadband tuner for receivingsignals having two different frequency bands.

BACKGROUND ART

[0002] A conventional tuner will be described below.

[0003] In the conventional tuner as shown in FIG. 4, input terminal 1receiving a high-frequency digital signal is connected to high-frequencyamplifier 2 for L band, the output of this high-frequency amplifier 2 isfed into bandpass filter 3 allowing L band frequency to pass through,and the output of this bandpass filter 3 and the output of localoscillator 4 oscillating a fixed frequency are fed into mixer 5.

[0004] The output of mixer 5 is connected to bandpass filter 6 allowingV band frequency to pass through. The output of bandpass filter 6 isconnected to one terminal 7 a of electronic changeover switch 7, whilethe output of tuning filter 10, to be described later, is connected tothe other terminal 7 b.

[0005] Input terminal 1 is connected also to high-frequency amplifier 8for V band, the output of this frequency amplifier 8 is fed intobandpass filter 9 allowing V band frequency to pass through, and theoutput of this bandpass filter 9 is fed into tuning filter 10.

[0006] Common terminal 7 c of changeover switch 7 is connected to oneinput of mixer 12, while the other input thereof is coupled with theoutput of local oscillator 11.

[0007] The output of mixer 12 is fed into 39-MHz bandpass filter 13 andthe output of this bandpass filter 13 is connected to output terminal14.

[0008] Further, local oscillator 11 is loop-connected to PLL circuit 15and this PLL circuit 15 is supplied with data from data terminal 16. Theoutput of PLL circuit 15 is also applied to the tuning terminal oftuning filter 10 via local oscillator 11.

[0009] Operation of the broadband tuner configured as above will bedescribed below.

[0010] When changeover switch 7 is turned to side 7 a in order that Lband is received, a high-frequency signal of L band supplied from inputterminal 1 is passed through bandpass filter 3 and mixed with the outputof local oscillator 4 in mixer 5 to be converted into V band frequency.This signal is passed through bandpass filter 6 and then mixed with theoutput of local oscillator 11 in mixer 12, whereby the signal ischannel-selected and, at the same time, converted into intermediatefrequency of 39 MHz. The intermediate frequency is put out from outputterminal 14 via bandpass filter 13 whose center frequency is 39 MHz.Here, the oscillation frequency of local oscillator 11 is controlled inPLL circuit 15 based on data supplied to data terminal 16; namely, thechannel selection is performed based on data supplied to data terminal16.

[0011] On the other hand, when changeover switch 7 is turned to side 7 bin order that V band is received, a high-frequency signal of V bandsupplied from input terminal 1 is passed through bandpass filter 9 and adesired wave is selected in tuning filter 10 for eliminating interferingwaves. The center frequency of tuning filter 10 is varied by the outputof PLL circuit 15 so that a desired frequency and frequencies in itsvicinity are passed therethrough.

[0012] The desired frequency is mixed with the output of localoscillator 11 in mixer 12, whereby the frequency is channel-selectedand, at the same time, converted into intermediate frequency of 39 MHz.This intermediate frequency is passed through bandpass filter 13 whosecenter frequency is 39 MHz and put out from output terminal 14. Here,the oscillation frequency of local oscillator 11 is controlled by PLLcircuit 15 based on data supplied to data terminal 16; namely, thechannel selection is performed based on data supplied to data terminal16.

[0013] Incidentally, the L band frequency here denotes radio waveshaving a bandwidth of approximately 300 MHz centering about 1.4 GHz andthe V band frequency here denotes radio waves having a bandwidth ofapproximately 100 MHz centering about 200 MHz.

[0014] In the conventional configuration as described above, however,since it operates as a single tuner in signal reception of V band, itrequired to have tuning filter 10 to eliminate image frequencyinterference. When such tuning filter 10 is employed, enormous amountsof manpower were required for adjustments of the same. Morespecifically, since the output of PLL circuit 15 is applied to localoscillator 11 and tuning filter 10 having their respectivevariable-capacitance diodes different from each other, frequencyvariations in separate diodes had to be adjusted with the same voltagefrom PLL circuit 15 by using inductance or the like, which took muchtime and hence there was the problem of increased manpower.

DISCLOSURE OF INVENTION

[0015] A broadband tuner is provided which comprises: an input terminalsupplied with a high-frequency digital signal; a first fixed filter,allowing L band frequency to pass through, connected to the inputterminal; a second fixed filter, allowing V band frequency to passthrough, connected to the input terminal; a first changeover switchhaving the output of the first fixed filter connected to one terminalthereof and the output of the second fixed filter connected to the otherterminal thereof; a first mixer having a common terminal of the firstchangeover switch applied to one input thereof and the output of a firstlocal oscillator connected to the other input thereof via a secondchangeover switch; a third fixed filter, allowing L band frequency topass through, connected to the output of the first mixer; a second mixerhaving the output of the third fixed filter applied to one input thereofand the output of a second local oscillator connected to the other inputthereof; an output terminal having the output of the second mixerapplied thereto; a first PLL circuit loop-connected to the first localoscillator; a first data terminal for supplying the first PLL circuitwith data; a second PLL circuit loop-connected to the second localoscillator; and a second data terminal for supplying the second PLLcircuit with data, in which, when the first changeover switch selectsthe output of the first fixed filter, the second changeover switch isturned off such that the first mixer is operated as an amplifier and theoscillation frequency of the second local oscillator is controlled basedon data supplied to the second data terminal, whereby the signal outputfrom the third fixed filter is channel-selected and converted into apredetermined frequency in the second mixer and, when the firstchangeover switch selects the output of the second fixed filter, thesecond changeover switch is turned on and the oscillation frequency ofthe first local oscillator is controlled based on data supplied to thefirst data terminal whereby a channel selection is performed while Vband frequency is converted into L band in the first mixer, and theoutput of the third fixed filter is converted into a predeterminedfrequency in the second mixer.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a block diagram of a broadband tuner in a firstpreferred embodiment of the present invention.

[0017]FIG. 2 is a block diagram of a broadband tuner in a secondpreferred embodiment of the present invention.

[0018]FIG. 3 is a block diagram of a broadband tuner in a thirdpreferred embodiment of the present invention.

[0019]FIG. 4 is a block diagram of a conventional broadband tuner.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Preferred embodiments of a broadband tuner according to thepresent invention will be described below with reference to theaccompanying drawings.

[0021] (Preferred Embodiment 1)

[0022]FIG. 1 is a block diagram of a broadband tuner of the preferredembodiment 1.

[0023] In FIG. 1, input terminal 21 receiving a high-frequency digitalsignal is connected to high-frequency amplifier 22 and the output ofthis high-frequency amplifier 22 is fed into fixed L bandpass filter 23allowing L band frequency to pass through. On the other hand, the outputof high-frequency amplifier 24 coupled with input terminal 21 isconnected to fixed V bandpass filter 25 allowing V band frequency topass through. The output of the aforesaid fixed filter 23 is coupled toone terminal 26 a of changeover switch 26, while the output of Vbandpass filter 25 is coupled to the other terminal 26 b. And commonterminal 26 c of changeover switch 26 is applied to one input of mixer29, while the output of local oscillator 27 is fed into the other inputof mixer 29 via changeover switch 28.

[0024] The output of mixer 29 is coupled to fixed L bandpass filter 30allowing L band frequency to pass through and, while the output of Lbandpass filter 30 is fed to one input of mixer 32, the output of localoscillator 31 is coupled to the other input.

[0025] The output of mixer 32 is coupled to a bandpass filter whosecenter frequency is 39 MHz and the output of this bandpass filter iscoupled to output terminal 33. Local oscillator 27 is loop-connected toPLL circuit 34 and this PLL circuit 34 is supplied with data from dataterminal 35. Further, local oscillator 31 is loop-connected to PLLcircuit 31 and this PLL circuit 36 is supplied with data from dataterminal 37.

[0026] Although a bandpass filter whose enter frequency is 1.4 GHz andbandwidth is 600 MHz is used here as L bandpass filter 23, it may be ahigh-pass filter allowing 1.1 GHz and above to pass through.

[0027] Although a bandpass filter whose center frequency is 200 MHz andbandwidth is 100 MHz is used here as V bandpass filter 25, it may be alow-pass filter allowing 300 MHz and below to pass through.

[0028] L bandpass filter 30 is a bandpass filter whose center frequencyis 1.4 GHz and bandwidth is 600 MHz.

[0029] Changeover switches 26 and 28 are electrically-switchable knownswitches formed of pin diodes or the like.

[0030] Output 39 of microcomputer 38 is connected to data terminal 35and data terminal 37. It is also connected to the switch controllingterminals of changeover switches 26 and 28. Input terminal 40 isconnected to microcomputer 38.

[0031] Operation of the broadband tuner configured as described abovewill be demonstrated below.

[0032] When changeover switch 26 is turned to side 26 a in order that Lband is received, changeover switch 28 is turned off and mixer 29operates as an amplifier for amplifying L band signal. Morespecifically, the high-frequency signal of L band fed from inputterminal 21, after being passed through L bandpass filter 23 andchangeover switch 26, is amplified by mixer 29 and passed through fixedfilter 30 of 1.4 GHz. This signal is mixed with the output of localoscillator 31 in mixer 32, whereby the signal is channel-selected and,at the same time, converted into intermediate frequency of 39 MHz. Theintermediate frequency is output from output terminal 33. Here, theoscillation frequency of local oscillator 31 is controlled in PLLcircuit 36 based on data fed to data terminal 37; that is, the channelselection is performed based on the data fed to data terminal 37.

[0033] Then, when changeover switch 26 is turned to side 26 b in orderthat V band is received, changeover switch 28 is turned on. Morespecifically, the high-frequency signal of V band fed from inputterminal 21, after being passed through V bandpass filter 25 andchangeover switch 26, is mixed with the output of local oscillator 27 inmixer 29, whereby the signal is channel-selected and, at the same time,converted into intermediate frequency of 1.4 GHz.

[0034] The intermediate frequency is passed through fixed filter 30whose center frequency is 1.4 GHz, converted into 39 MHz in mixer 32,and put out from output terminal 33. In this case, the oscillationfrequency of local oscillator 27 is controlled in PLL circuit 34 basedon data fed to data terminal 35; namely, the channel selection isperformed based on the data fed to data terminal 35.

[0035] According to the present preferred embodiment 1, as describedabove, a double superheterodyne configuration by the use of mixer 29 andmixer 32 is provided for reception of V band frequency. Therefore, it isfree from interference of the image frequency even if tuning filter 10as in the conventional case shown in FIG. 4 is not used. Accordingly,the need for manpower for adjusting tuning filter 10 can be cut down.

[0036] Further, since the need for mounting tuning filter 10 iseliminated, reduction in size and manpower can be attained.

[0037] Further, both frequency bands of V band and L band can bereceived by switching between changeover switches 26 and 28.

[0038] Furthermore, though a double superheterodyne configuration isadopted, the number of mixers is not increased from that in theconventional art.

[0039] It is possible to have mixer 29, local oscillator 27, PLL circuit34, mixer 32, local oscillator 31, PLL circuit 36, changeover switch 26,and changeover switch 28 integrated into one package. By suchintegration, reduction in size and increase in reliability can beattained.

[0040] Further, by adapting microcomputer 38 to control PLL circuit 34,PLL circuit 36, changeover switch 26, and changeover switch 28,controlling of these members can be easily performed by externallychanging data fed to input terminal 40.

[0041] (Preferred Embodiment 2)

[0042] The broadband tuner in the preferred embodiment 2 is such thateliminates image interference by using two mixers and two 90-degreephasers instead of mixer 32 used in the preferred embodiment 1.

[0043] In FIG. 2, high-frequency amplifier 42 is connected to inputterminal 41 receiving a high-frequency digital signal and the output ofhigh-frequency amplifier 42 is fed into fixed filter 43 allowing L bandfrequency to pass through.

[0044] Further, the output of high-frequency amplifier 44 connected toinput terminal 41 is coupled to fixed filter 45 allowing V bandfrequency to pass through.

[0045] Then, while the output of fixed filter 43 is coupled to oneterminal 46 a of changeover switch 46, the output of fixed filter 45 iscoupled to the other terminal 46 b, and common terminal 46 c ofchangeover switch 46 is input to AGC amplifier 47. While the output ofAGC amplifier 47 is fed to one input of mixer 50, the output of localoscillator 48 is fed to the other input via changeover switch 49.

[0046] The output of mixer 50 is connected to fixed filter 51 allowing Lband frequency to pass through and the output of this fixed filter 51 isinput to AGC amplifier 52. The output of AGC amplifier 52 is fed to oneinput of mixer 55, while the output of local oscillator 53 is fed to theother input via 90-degree phaser 54.

[0047] Further, the output of AGC amplifier 52 is fed to one input ofmixer 56, while local oscillator 53 is connected to the other input.

[0048] Ninety-degree phaser 57 is connected between the output of mixer55 and the output of mixer 56, the output of mixer 56 is input to fixedfilter 58, the output of this fixed filter 58 is input to AGC amplifier59, and the output of this AGC amplifier 59 is fed to output terminal60.

[0049] While PLL circuit 61 is loop-connected to local oscillator 48 anddata is fed into this PLL circuit 61 from data terminal 62, PLL circuit63 is loop-connected to local oscillator 53 and data is fed into thisPLL circuit 63 from data terminal 64.

[0050] Operation in the broadband tuner configured as described abovewill be demonstrated below. Point in the preferred embodiment 2different from that in the preferred embodiment 1 is as follows: thatis, while one portion of the output of AGC amplifier 52 connected to theoutput of fixed filter 51 is put out via mixer 56 and the other portionis put out via mixer 55, these output portions are rendered 180 degreesout of phase with each other by two 90-degree phasers 54 and 57, andthereby interfering waves are eliminated. Otherwise, this embodiment isthe same as preferred embodiment 1.

[0051] More particularly, when the output of fixed filter 43 is selectedby changeover switch 46, changeover switch 49 is turned off and mixer 50is operated as an amplifier. Then, the oscillation frequency of localoscillator 53 is controlled based on data fed to terminal 64 and,thereby, the signal output from fixed filter 51 is channel-selected and,at the same time, converted into a predetermined frequency in mixer 56and mixer 55. This signal is put out from output terminal 60 via fixedfilter 58.

[0052] On the other hand, when the output of fixed filter 45 is selectedby changeover switch 46, changeover switch 49 is turned on and theoscillation frequency of local oscillator 48 is controlled based on datafed to data terminal 62, whereby frequency of V band is converted into Lband and a channel selection is performed at the same time in mixer 50.The output of fixed filter 51 is converted into a predeterminedfrequency in mixer 55 and mixer 56 and put out from output terminal 60via fixed filter 58.

[0053] Thus, in reception of V band frequency, a double superheterodyneconfiguration is provided by the use of mixer 50, as well as mixer 55and mixer 56. Hence, it is made free from interference of the imagefrequency even if a tuning filter is not employed. Therefore, the needfor manpower for adjusting the tuning filter can be eliminated.

[0054] Further, since a tuning filter is not required to be mounted,reduction in size and manpower can be attained.

[0055] Further, in reception of L band, the output of mixer 56 iscoupled with a signal rendered 180 degrees out of phase via two90-degree phasers. Hence, image interfering frequencies can beeliminated.

[0056] Further, either of V band and L band frequencies can be receivedby switching between changeover switches 46 and 49.

[0057] Here, though a bandpass filter whose center frequency is 1.4 GHzand bandwidth is 600 MHz is used as fixed filter 43, it may be ahigh-pass filter allowing frequencies above 1.1 GHz to pass through.

[0058] Though a bandpass filter whose center frequency is 200 MHz andbandwidth is 100 MHz is used as fixed filter 45, it may be a low-passfilter allowing frequencies below 300 MHz to pass through.

[0059] Fixed filter 51 is such a bandpass filter that has a centerfrequency of 1.4 GHz and a bandwidth of 600 MHz.

[0060] Fixed filter 58 is such a bandpass filter that has a centerfrequency of 39 MHz and a bandwidth of 6 MHz.

[0061] Changeover switches 46 and 49 are electronically-switchable knownswitches formed of pin diodes and the like.

[0062] Input terminal 65 of AGC control voltage, coupled with AGCamplifiers 47, 52, and 59, is externally controlled.

[0063] (Preferred Embodiment 3)

[0064] The broadband tuner of the preferred embodiment 3 is such that isswitchable between an IF outputting tuner using two mixers and two90-degree phasers, instead of mixer 32 of the preferred embodiment 1,for eliminating image interference and an IQ detecting tuner using twomixers.

[0065] In FIG. 3, input terminal 71 is supplied with a high-frequencydigital signal, this input terminal 71 is connected to fixed filter 73allowing L band frequency to pass through via high-frequency amplifier72, and input terminal 71 is also connected to fixed filter 75 allowingV band frequency to pass through via high-frequency amplifier 74.

[0066] The output of fixed filter 73 is connected to one terminal 76 aof changeover switch 76, the output of fixed filter 75 is connected tothe other terminal 76 b, and common terminal 76 c of changeover switch76 is fed into AGC amplifier 77. The output of AGC amplifier 77 iscoupled to one input of mixer 80 and the output of local oscillator 78is fed into the other input via changeover switch 79.

[0067] The output of mixer 80 is connected to fixed filter 81 allowing Lband frequency to pass through and this fixed filter 81 is fed into AGCamplifier 82. The output of AGC amplifier 82 is connected to one inputof mixer 85, while the output of local oscillator 83 is connected to theother input via 90-degree phaser 84. The output of mixer 85 is connectedto AGC amplifier 87 via low-pass filter 86 and the output of AGCamplifier 87 is put out to output terminal 89.

[0068] The output of AGC amplifier 82 is connected to one input of mixer90, while the output of local oscillator 83 is connected to the otherinput.

[0069] A series connection of 90-degree phaser 91 and changeover switch92 is connected between the output of mixer 85 and the output of mixer90. Common terminal 93 c of changeover switch 93 is connected to theoutput of mixer 90, one terminal 93 a of changeover switch 93 isconnected to low-pass filter 94, and the output of low-pass filter 94 isconnected to AGC amplifier 95. The output of AGC amplifier 95 isconnected to output terminal 96. Bandpass filter 97 is connected betweenthe other terminal 93 b of changeover switch 93 and low-pass filter 94.PLL circuit 98 is loop-connected to local oscillator 78 and this PLLcircuit 98 is supplied with data from data terminal 99. PLL circuit 100is loop-connected to local oscillator 83 and this PLL circuit 100 issupplied with data from data terminal 101.

[0070] Relationship between changeover switches 92 and 93 will bedescribed below. Referring to the relationship, there is a firstoperation mode, in which changeover switch 92 is turned off andchangeover switch 93 is turned to the side of one terminal 93 a, i.e.,to the side of low-pass filter 94, and a second operation mode, in whichchangeover switch 92 is turned on and changeover switch 93 is turned tothe side of the other terminal 93 b, i.e., to the side of bandpassfilter 97.

[0071] Control terminal 102 is for externally controlling gains in AGCamplifiers 77, 82, 87, and 95.

[0072] Here, changeover switches 92 and 93 are adapted to beelectronically switched by pin diodes and these are operated interlockedwith each other. More specifically, in the first operation mode,changeover switch 92 is turned off and changeover switch 93 is connectedto the side of one terminal 93 a, i.e., to the side of low-pass filter94. Accordingly, the tuner in the present preferred embodiment 3operates as an IQ detection tuner, in which I signal is put out fromoutput terminal 89 and Q signal is put out from output terminal 96.

[0073] On the other hand, in the second operation mode, changeoverswitch 92 is turned on and changeover switch 93 is turned to the side ofthe other terminal 93 b, i.e., to the side of bandpass filter 97.Accordingly, the tuner in the present preferred embodiment 3 operates asan IF signal outputting tuner, in which IF signal is put out from outputterminal 96.

[0074] Ninety-degree phasers 84 and 91 are phasers causing a delay inthe phase by ninety degrees. Since, in the IF tuner, the output of mixer85 is passed through 90-degree phasers 84 and 91 in series, it is, afterall, delayed 180 degrees when it is combined with the output of mixer90. Thus interference signals can be eliminated.

[0075] In the IQ detection tuner, baseband signals are put out fromoutput terminals 89 and 96. In the IF outputting tuner, an IF signal ofapproximately 400 MHz is put out from output terminal 96.

[0076] In the preferred embodiment 3, although the signal fed to inputterminal 71 was said to be ground wave signal approximately between 50MHz and 860 MHz, it may be digital satellite broad cast signalapproximately between 950 MHz and 2.2 GHz. At this time, the centerfrequency of bandpass filter 81 is such that passes each band andattenuates undesired band. The output of mixer 80 is set to intermediatefrequency of 1.4 GHz or 1.2 GHz. Hence, bandpass filter 81 also allowsthe above frequency to pass through.

[0077] The cutoff frequency of low-pass filters 86 and 94 is around 50MHz, the center frequency of bandpass filter 97 is around 400 MHz, andits bandwidth is around 30 MHz.

[0078] Further, since the circuit of the present preferred embodiment 3is formed of balanced circuits, a tuner immune to noise interference canbe obtained.

[0079] Since the tuner can be used as two kinds of tuners, reduction inmanpower can be attained by integrating these circuits in massproduction. Miniaturization can also be attained by the integration.

[0080] In the process of manufacturing, changeover switches 92 and 93may be changeably produced by changing manner of mounting of a jumperresistor. Then, it can be fixed beforehand whether IF outputting tuneror IQ detection tuner is produced and, hence, it is not necessary tochange one to the other afterward. Throughout preferred embodiments 1,2, and 3, by having at least mixers and local oscillators formed ofbalanced circuits and integrated, antinoise performance can be improved.Further, by integrating circuits with mixers and local oscillatorsformed of silicon, germanium elements, tuners can be provided withdecreased manpower.

[0081] According to the present invention as described above, there isprovided a double superheterodyne configuration using a first mixer anda second mixer for reception of V band frequency. Hence, interference ofthe image frequency can be eliminated without using a tuning filter.Accordingly, manpower for adjusting the tuning filter becomesunnecessary.

[0082] Further, since a tuning filter is not required to be mounted,reduction in size and manpower can be attained.

[0083] Further, both V band and L band frequency bands can be receivedby switching therebetween with changeover switches.

[0084] Further, although there is provided a double superheterodyneconfiguration, the number of mixers is kept as before.

INDUSTRIAL APPLICABILITY

[0085] The present invention relates to a broadband tuner capable ofreceiving two different frequency bands.

[0086] Since, in the present invention, a double superheterodyneconfiguration using a first mixer and a second mixer is provided forreception of V band frequency, interference of image frequencies can beavoided without using a tuning filter and, hence, reduction in size andmanpower can be attained.

LIST OF REFERENCE NUMERALS IN THE DRAWINGS

[0087]21 Input terminal

[0088]23 L bandpass filter

[0089]25 V bandpass filter

[0090]26 Changeover switch

[0091]27 Local oscillator

[0092]28 Changeover switch

[0093]29 Mixer

[0094]30 L bandpass filter

[0095]31 Local oscillator

[0096]32 Mixer

[0097]33 Output terminal

[0098]34 PLL circuit

[0099]35 Data terminal

[0100]36 PLL circuit

[0101]37 Data terminal

1. A broadband tuner comprising: an input terminal supplied with ahigh-frequency digital signal; a first fixed filter, allowing L bandfrequency to pass through, connected to said input terminal; a secondfixed filter, allowing V band frequency to pass through, connected tosaid input terminal; a first changeover switch having an output of saidfirst fixed filter connected to one terminal thereof and an output ofsaid second fixed filter connected to the other terminal thereof; afirst mixer having a common terminal of said first changeover switchapplied to one input thereof and an output of a first local oscillatorconnected to the other input thereof via a second changeover switch; athird fixed filter, allowing L band frequency to pass through, connectedto an output of said first mixer; a second mixer having an output ofsaid third fixed filter applied to one input thereof and an output of asecond local oscillator connected to the other input thereof; an outputterminal having an output of said second mixer applied thereto; a firstPLL circuit loop-connected to said first local oscillator; a first dataterminal for supplying said first PLL circuit with data; a second PLLcircuit loop-connected to said second local oscillator; and a seconddata terminal for supplying said second PLL circuit with data, wherein,when said first changeover switch selects the output of said first fixedfilter, said second changeover switch is turned off such that said firstmixer is operated as an amplifier and an oscillation frequency of saidsecond local oscillator is controlled based on data supplied to saidsecond data terminal, whereby a signal output from said third fixedfilter is channel-selected and converted into a predetermined frequencyin said second mixer, and when said first changeover switch selects theoutput of said second fixed filter, said second changeover switch isturned on and an oscillation frequency of said first local oscillator iscontrolled based on data supplied to said first data terminal, whereby achannel selection is performed while the V band frequency is convertedinto L band in said first mixer, and an output of said third fixedfilter is converted into a predetermined frequency in said second mixer.2. The broadband tuner according to claim 1, wherein said first mixer,said first local oscillator, said first PLL circuit, second mixer,second local oscillator, second PLL circuit, first changeover switch,and second changeover switch are integrated into one package.
 3. Thebroadband tuner according to claim 1 further comprising a microcomputerfor controlling said first data terminal, said second data terminal,said first changeover switch, and said second changeover switch.
 4. Abroadband tuner comprising: an input terminal supplied with ahigh-frequency digital signal; a first fixed filter, allowing L bandfrequency to pass through, connected to said input terminal; a secondfixed filter, allowing V band frequency to pass through, connected tosaid input terminal; a first changeover switch having an output of saidfirst fixed filter connected to one terminal thereof and an output ofsaid second fixed filter connected to the other terminal thereof; afirst mixer having a common terminal of said first changeover switchapplied to one input thereof and an output of a first local oscillatorconnected to the other terminal thereof via a second changeover switch;a third fixed filter, allowing L band frequency to pass through,connected to an output of said first mixer; a second mixer having anoutput of said third fixed filter applied to one input thereof and anoutput of a second local oscillator connected to the other input thereofvia a first 90-degree phaser; a third mixer having the output of saidthird fixed filter applied to one input thereof and the output of saidsecond local oscillator connected to the other input thereof; a second90-degree phaser connected between an output of said second mixer and anoutput of said third mixer; a fourth fixed filter connected to an outputof said third mixer; an output terminal supplied with an output of saidfourth fixed filter, a first PLL circuit loop-connected to said firstlocal oscillator; a first data terminal supplying said first PLL circuitwith data; a second PLL circuit loop-connected to said second localoscillator; and a second data terminal supplying said second PLL circuitwith data, wherein, when said first changeover switch selects an outputof said first fixed filter, said second changeover switch is turned offsuch that said first mixer is operated as an amplifier and anoscillation frequency of said second local oscillator is controlledbased on data input to said second data terminal, whereby a desiredchannel is selected and converted into a predetermined frequency in saidsecond mixer and said third mixer, and when said first changeover switchselects an output of said second fixed filter, said second changeoverswitch is turned on and an oscillation frequency of said localoscillator is controlled based on data supplied to said first dataterminal, whereby a channel selection is performed while the V bandfrequency is converted into L band in said first mixer, and an outputfrom said third fixed filter is converted into a predetermined frequencyin said second mixer and said third mixer.
 5. A broadband tunercomprising: an input terminal supplied with a high-frequency digitalsignal; a first fixed filter, allowing L band frequency to pass through,coupled to said input terminal; a second fixed filter, allowing V bandfrequency to pass through, coupled to said input terminal; a firstchangeover switch having an output of said first fixed filter connectedto one terminal thereof and an output of said second fixed filterconnected to the other terminal thereof; a first mixer having a commonterminal of said first changeover switch applied to one input thereofand an output of first local oscillator coupled to the other inputthereof via a second changeover switch; a third fixed filter suppliedwith an output of said first mixer and allowing L band frequency to passthrough; a second mixer having an output of said third fixed filterapplied to one input thereof and an output of a second local oscillatorcoupled to the other input thereof via a first 90-degree phaser; afourth fixed filter coupled with an output of said second mixer; a firstoutput terminal supplied with an output of said fourth fixed filter; athird mixer having the output of said third fixed filter applied to oneinput thereof and the output of said second local oscillator coupled tothe other input thereof; a series connection of a second 90-degreephaser and a third changeover switch connected between an output of saidsecond mixer and an output of said third mixer; a fifth fixed filtercoupled to the output of said third mixer; a second output terminalcoupled with an output of said fifth fixed filter; a first PLL circuitloop-connected to said first local oscillator; a first data terminalsupplying said first PLL circuit with data; a second PLL circuitloop-connected to said second local oscillator; and a second dataterminal supplying said second PLL circuit with data, wherein saidbroadband tuner has a first operation mode in which said thirdchangeover switch is turned off and a second operation mode in whichsaid third changeover switch is turned on, and wherein, when said firstchangeover switch selects an output of said first fixed filter, saidsecond changeover switch is turned off such that said first mixer isoperated as an amplifier and the oscillation frequency of said secondlocal oscillator is controlled based on data input to said second dataterminal, whereby a signal output from said third fixed filter ischannel-selected and converted into a predetermined frequency in saidsecond mixer and third mixer, and, when said first changeover switchselects an output of said second fixed filter, said second changeoverswitch is turned on and oscillation frequency of said first localoscillator is controlled based on data input to said first dataterminal, whereby a channel selection is performed while the V bandsignal is converted into L band, and the same is converted into apredetermined frequency in said second mixer and said third mixer. 6.The broadband tuner according to claim 5, wherein said fourth fixedfilter and said fifth fixed filter are formed of low-pass filter, thereis provided a bandpass filter selectably switchable with said fifthfixed filter, and said fifth fixed filter is selected in the firstoperation mode and said bandpass filter is selected in the secondoperation mode.
 7. The broadband tuner according to claim 5, wherein thefirst operation mode and the second operation mode are switchedtherebetween by changing manner of mounting of a jumper resistor.
 8. Thebroadband tuner according to claim 5, wherein at least one of said firstto third mixers and said first to second local oscillator is formed of abalanced circuit and integrated circuited.
 9. The broadband tuneraccording to claim 5, wherein at least one of said first to third mixersand said first to second local oscillator is formed of a silicon,germanium device and integrated circuited.